The present invention has utility in troubleshooting and repairing electronic circuit board assemblies where electronic components are soldered directly in place.
It is known that various faults in a circuit board assembly may be isolated by measuring the resistance between selected points or nodes. A faulty integrated circuit will resistively pull down a node to which it is electrically connected. Improper resistance readings indicate that a fault exists within the assembly. A technician can then use repair procedures in an attempt to isolate the faulty part, remove it by de-soldering, confirm the fault is cleared, and replace the component with a good one. However, attempts to isolate the fault are complicated by the number of resistances that may be connected to the faulty node. The lowest resistance present will dominate the node and make finding the fault difficult.
In production environments, it is desirable to isolate faults quickly and accurately in order to minimize the amount of labor required to correct the fault, thus reducing the cost of manufacture. It is also desirable to be able to identify faulty components on circuit board assemblies in as short a test cycle as possible, i.e. within a maximum of several hours rather than several days, because in this manner the odds of correlating component faults to a particular batch of faulty component supplies is much greater, and such faulty components can be immediately isolated, re-tested, and, if necessary, removed from the production of further circuit board assemblies, thereby resulting in significant labor and piece-part savings.
It is also desirable to minimize the amount of de-soldering of components from the board to limit possible damage to the circuit board and to adjoining components. By minimizing the de-soldering of components, manufacturing costs can be significantly reduced. For example, if the average cost to manufacture a circuit board is $2,500, and a typical quality control procedure requires that a board must be scrapped if more than 3 components must be re-soldered, then a significant reduction in the number of scrapped boards would result if components did not have to be de-soldered to be tested. Moreover, for circuit boards onto which components have been surface-mounted it is difficult, if not impossible, to de-solder components to test them, due to the malleability limitations of their leads.